The present invention pertains to a technical field where image reading apparatuses are utilized for digital photoprinters for photoelectrically reading images recorded on films to obtain prints. (photographs) that are reproduced from the images.
Images recorded on photographic films (hereinafter called the films) such as negative films, reversal films and the like are mainly printed out on photosensitive material (photographic paper) by projecting the on-film image onto the photosensitive material so that the photosensitive material is subjected to surface exposure or so-called direct exposure (analog exposure).
On the other hand, printing apparatuses utilizing digital exposure have been put to practical use in recent years. More specifically, a digital photoprinter is used for printing out (finishing off) an image recorded on a film through the steps of reading the image photoelectrically, converting the read-out image into a digital signal, performing various kinds of image processing in order to obtain image data to be recorded and subjecting photosensitive material to scanning exposure by means of the recording light modulated according to the image data, to thereby record the image (latent image).
As exposure conditions at the time of printing can be determined by processing images with digital data as image data in the digital photoprinter, high-grade prints that have been unavailable until now become obtainable by such as making compensation for image fade-out and improper gradation such as washed-out highlight and dull shadow originating from backlight, electronic flashing and the like, sharpness processing, compensation for color or density failure. Moreover, a composite photograph using a plurality of images, image division, a composition of characters and the like can be attained by processing the image data. The image data processing also makes it possible to output edited/processed prints freely in accordance with an intended use.
Furthermore, the digital photoprinter makes image data applicable for other purposes than photography, since the photoprinter allows images to be outputted as prints (photographs) and also allows the image data to be not only supplied to a computer, for example, but also stored in, optical and/or magnetic recording media such as floppy disks.
Such a digital photoprinter as described above essentially comprises an image input apparatus having a scanner (image reading apparatus) for reading an image recorded on a film photoelectrically and an image-processing apparatus for subjecting the read-out image to image processing in order to provide output image data (exposure conditions), and an image output apparatus having a printer (image recording apparatus) for recording a latent image by subjecting photosensitive material to scanning exposure according to the image data outputted from the image input apparatus and a processor (developing apparatus) for subjecting the exposed photosensitive material to developing processing for printing purposes.
The operation of the scanner includes making read light emitted from a light source incident on a film to obtain projected light for carrying an image projected on, the film, effecting image formation in an image sensor such as a charge coupled device (CCD) by means of an image forming lens so as to read the image by subjecting the projected light to photoelectric conversion, performing various kinds of image processing as the occasion demands and sending data concerning the on-film image (image data signal) to the image-processing apparatus.
The operation of the image-processing apparatus includes setting image processing conditions according to the image data read by the scanner, applying image processing corresponding to the set conditions to the image data and sending output image recording data (exposure conditions) to the printer.
The operation of the printer, that is, a printer utilizing light beam scanning exposure, for example, includes modulating a light beam according to the image data sent from the image-processing apparatus, deflecting the light beam in the main scanning direction, transporting the photosensitive material in an auxiliary scanning direction perpendicular to the main scanning direction in order to form a latent image by exposing (printing) the photosensitive material, using the tight beam that carries the image therewith and performing developing processing corresponding to the photosensitive material in the processor in order to make a print (photograph) reproduced from the on-film image.
As an image reading method at a digital photoprinter, a surface exposure method, in which first a read light is irradiated all over a frame of a film, and then the projected light is read through each of red (R), green (G), and blue (B), filters intercharged each other in order by an area sensor photoelectrically, is known in the art. Another method, i.e., a slit scanning method, in which first line sensors for respective reading of R, G, and B are used, and secondly a read light in a slit formed in parallel to the extending direction (main scanning direction) of the line sensors is incident on the film, and then the film is transported (or an optical system is moved) in the longitudinal direction of the film, or in the auxiliary scanning direction perpendicular to the main scanning direction, and finally whole area of the frame of the film is read by slit scanning, is also known in the art.
The surface exposure method and the slit scanning method each have advantages and disadvantages. An area sensor is generally high in cost, since it contains a number of photoelectric transducers, and CCD cells. Particularly, if a reproduction image of high quality is required, it is necessary to employ an area sensor containing a large number of cells equal to or proportional to the squared number of the resolution, in order to read the original image in higher resolution.
Moreover, an area sensor supplied in the market as a product sometimes contains a small number of defective cells, so-called defective pixel cells, which fail to output accurate signals in accordance with a quantity of the incident light. The area sensor including the defective pixel cells is often found among the area sensors which have been produced at a some high yield rate. This necessitates a complicated correction circuit to compensate errors caused by the defective cells including defective pixels.
As a result, reading by the slit scanning method is more advantageous from the standpoint of cost.
In order to obtain a reproduction image of high quality, which properly has reproduced an original image, in the case of reading the image by the scanner, it is necessary to read a whole density range of the original image with the highest possible resolution, and it is preferable to read with the widest possible dynamic range. In order to accomplish this, for example, when a photograph film is read out, a so-called density control is performed in such a way that the image reading is carried out under a condition that an image sensor is saturated at a density just equal to or merely lower than the lowest density of the original image on the photograph film.
Moreover, when one color occupies a large area of an image, like an image of a subject taken on a green of a golf course, or an image of a person""s face taken in front of wall paper with a bright color, so-called color failure occurs so that a reproduction image comes out with unnatural colors or tints. This color failure may be corrected by image processing to some extent. However, since the correction by image processing is limited, it is preferable to control color balance of the image (image data) when the original image is read. This will enable to obtain a reproduction image of high quality reliably.
Therefore, read conditions of a scanner should be controlled with regard to the density and the color balance of the original image whenever each of three colors is read, in order to obtain a reproduced image of high quality reliably. The output image data thus obtained must have a wide dynamic range and a good color balance.
At the image reading by the surface exposure, each of R, G, and B is read in order by utilizing a variable diaphragm. It is possible to read original images with a wide dynamic range of density and a good color balance by controlling the light quantity of read light when each of R, G, and B is read.
On the other hand, at the image reading by the slit scanning, it is possible to control density by controlling light quantity of read light by utilizing a variable diaphragm, since a projected light forms images on line sensors concurrently corresponding to three primary colors or more colors, but impossible to obtain a good color balance among R, C, and B.
Furthermore, a number of images are shot in succession in 24 or 36 frames, for example, on a film which is mainly used as original for a digital photoprinter. In case of, so-called, printing with film processing, prints are made by reading out each frame in order.
At image reading by the surface exposure, it is possible to determine conditions such as of a diaphragm during an interval while a frame moves to another, since the images are read at each predetermined position in order while each frame stops.
On the other hand, at image reading by the slit scanning, images are read while the film is moving, that is, while frames are moving. Moreover, it is preferable to read images without stopping the film until the image reading of the last frame is over in order to perform an efficient image reading and to put the lower possible load on the film transport system. Furthermore, it is also preferable to maintain the transport speed of a film as fast as possible within the capacity of such as image sensors and image processing in order to increase productivity. However, since a space between frames is generally so narrow as 1-2 mm, it is difficult to make a minute adjustment or control of the variable diaphragm during the interval between frames.
Accordingly, it is an object of the present invention to be capable of solving the above-mentioned problems in the art, and to provide an image reading apparatus for reading an original image by a slit scanning employing line sensors for corresponding to respective image reading of R, G, and B which are capable of reading, at high efficiency, the image that is adjusted to have a wide dynamic range and a good color balance in accordance with the original image; and also which capable of outputting a reproduced image of high quality at constantly high productivity by such as a digital photoprinter.
To achieve the above object, the present invention provides an image reading apparatus for reading an original image photoelectrically. The image reading apparatus comprises a light source for irradiating read light, a holder for holding an original having the original image in a predetermined read position, a light quantity controller for controlling quantity of read light incident on the original, an image sensor having a row of line sensors with regard to three primary colors or more colors with each line sensor corresponding to each primary color or each color and comprising a plurality of photoelectric transducing elements arranged in a direction, a scanner for relatively moving the original and an optical system in an auxiliary scanning direction perpendicular to the direction of element arrangement of the line sensor, and an adjuster for adjusting read conditions of the image sensor in each line sensor independently.
The original is preferably a long photographic strip of film. The holder and the scanner compose a film carrier. It is preferable that the carrier moves the photographic film in its longitudinal direction, coincident with the auxiliary scanning direction while holding the long photographic film on the read position. It is also preferable that the carrier can be loaded on and unloaded from a predetermined position.
It is preferable that the light quantity controller mainly controls density of the original image, while the adjuster mainly adjusts with regard to a color balance of the original image.
Moreover, the read conditions adjusted by the adjuster are with regard to the light quantity. Resolving power of the adjustment by the adjuster is preferably higher than that of the light quantity control by the light quantity controller.
Furthermore, the apparatus preferably has a color adjuster for adjusting color components of the read light.
Furthermore, the light quantity controller is preferably a diaphragm. The line sensor is preferably a line CCD sensor. The adjuster preferably adjusts an accumulated time of the line CCD sensor.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.